Version 5.0.0-alpha1, an experimental pre-release.
Think on backup.
https://www.gramps-project.org/wiki/index.php?title=How_to_make_a_backup
Changes since '4.2.3':
See change log: https://gramps-project.org/bugs/changelog_page.php?version_id=86
Announcement:
http://gramps.1791082.n4.nabble.com/Re-Gramps-5-0-alpha-announcement-draft-td4675918.html